The MID Server role has changed significantly in the Fuji release of ServiceNow. In all previous versions, the MID was a connector that simply forwarded everything it received from the probes to the target instance. Starting with Fuji, the MID Server has a much more significant role; it now processes up to two or three “on after” scripts for a number of probes (previously sensor scripts) and then transmits a smaller payload to the instance. The result is a memory usage of 100% at 512MB by default.
To address this increase in the load on the MID Server, you can adjust the allowable memory usage by editing the wrapper-override.conf file, typically at line 35, by uncommenting the line and increasing the java.maxmemory from the 512MB default to 1024MB. ServiceNow is now considering updating the MID Server host requirements by a factor of two to address this change. Additionally, to take advantage of the increase in available memory, you should increase the number of threads used in the MID Server Configuration Parameters from 25 to 50 and monitor those threads until you determine how many you need for optimal performance.
As a result of these changes, the best practice is NOT to install multiple MID Server agents on the same host when both of those agents are configured to communicate with the same instance (i.e. “prod.servicenow.com” minimum requirements for the MID Server should be doubled). We used to help people maximize a host OS’s resources by putting more than one MID Server application on a single host server to consume more CPU and RAM, but that is no longer necessary. If you have implemented MID Servers that way today, begin to consider removing those MID Servers from the mix.
Original MID Server Host Specs Pre-Fuji Release
For all versions of ServiceNow prior to Fuji, the minimum suggested configuration for MID Servers is:
4GB of available RAM per application
2+GHZ CPU (Multi-core preferred)
500MB of disk space per application deployed
Can ride-along with other services (dependent on server utilization and resource availability)
New MID Server Host Specs Starting in the Fuji Release
For the Fuji release onward, the minimum suggested configuration for MID Servers is:
8GB of available RAM per application
2+GHZ CPU (Quad-core preferred)
1 GB of disk space per application deployed
My Recommendations
After having installed over 500 MID Servers in my career, I have built up a considerable amount of experience in balancing MID Servers for various uses. The following is a lowest common denominator of what I think should be done for a base MID Server installation.
1) Device (VM or Hardware) Configuration (requirements I’ve followed since 2012):
4GB minimum (8GB preferred)
2 CPU (Quad preferred)
40GB disk space (Win 2008 R2 + MID Server(s))
35-40 Threads (25 is the current default). You’ll need to adjust this during a load test to keep it at less than 100% utilization. Remember, more threads equals more utilization. (Note: The more threads needed, the more CPUs recommended.)
Multiple MID Servers on the same box ONLY if it is a DEV/QA box (no regular loading). DO NOT DO THIS FOR PRODUCTION!
2) VM Constraints
Make sure that when you’re using a VM, the box on which it resides does not have a high-utilization VM residing alongside it. This setup constrains the actual CPU, memory and disk utilization and creates the possibility that you will run into shared network connection blocking issues. I only had this happen once, but that was all it took to learn my lesson.
3) Directories
Be sure to change your working directory from Windows temp to a custom directory AND exclude that new directory from any virus scanners running on the box. Scanning the default directory can lead to a massive performance hit.
4) Load Balancing Order Number
When load balancing, remember to change the order number for each MID Server! The best practice for load balancing is to configure MID Servers on separate hosts and associate them with a cluster. In the cluster configuration page, be sure to change the order from the default value to 100, 200, 300, etc. for load balancing.
As a result of the new functionality of the MID Server in the Fuji release, the practice of sharing a MID Server between Discovery and an integration point will most likely result in poor performance during any overlapping processes. Therefore, when working in the Fuji release, you should avoid using multiple MID Server hosts.
Additional Resources
For more on using MID Servers, check out these additional resources:
- ServiceNow Discovery 101: Virus Scanners And MID Server Performance
- ServiceNow Discovery 101: Discovery Schedules Best Practices
- MID Server Clusters for Load Balance and Fail-over
Plus, be sure to review our top 10 best practices for ServiceNow Discovery
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